1. Field of the Invention
The invention lies in the field of network structures for signal transmission such as, e.g., network structures based on passive optical networks (PONs), in which there are included network elements for setting up and maintaining interconnections between signal-transmission lines. More in particular, it relates to an interconnect apparatus for interconnecting at least one signal-input port with a number of signal-output ports by way of a signal bus.
2. Prior Art
Currently, network architectures are being developed which are called SuperPONs, as described in, e.g., reference [1]. A SuperPON is an APON (ATM over Passive Optical Networks) having optical amplifiers in order to make possible a high splitting rate and a wide range. An APON is a passive optical network in which signal transport takes place on the basis of ATM [=Asynchronous Transfer Mode], as described in, e.g., reference [2]. An essential "component" in a SuperPON is a local node having a combined amplification and splitting function. In such a local node, communication signals, which originate from a main node having a switching function and which are supplied by way of a "feeder", are amplified, if so required, and distributed among a number of passive optical networks having great numbers of connecting options for network users. The communication signals may be supplied as optical signals by way of an optical feeder. The communication signals may also be supplied as electric signals having, e.g., an SDH [=Synchronous Digital Hierarchy] transmission system as feeder, the local node also having an OLT function (OLT=Optical Line Termination). Networks of such size, however, require a high degree of flexibility regarding extendibility in numbers of connections and/or in capacity per connection. Said flexibility is particularly important for introducing wide-band services by way of optical links to home connections in the event of a rising number of users and a demand for more capacity per user. In addition, interrupt times in the event of implementing extensions should, if not be left out, at least be limited as far as possible. Such flexibility may be achieved if, in such a local node, there is placed an interconnect apparatus having an already-installed interconnect capacity which is tuned to the future, at any rate prepared for actual installation, of which capacity originally only a limited portion is used. One of the requirements here is that the interconnect apparatus permit segmentation of the original network, i.c. a SuperPON, in a relatively simple manner. This is to say that the network may be split up into two (or more) separate parts which by itself again form a network of the same type, in this case a SuperPON having its own connection to the feeder. In order to achieve flexibility in interconnection, there are known apparatus based on a rack structure, such as a backplane structure, provided with a signal bus and with a number of module positions. At said module positions, there may be plugged in circuit modules in the form of, e.g., plug-in boards, with electric and/or optical circuits having various signal-processing functions or I/O functions, as a result of which there are realised mutual interconnections between the circuit modules by way of the signal bus. Basically, the circuit modules are easy to exchange. Such an interconnect apparatus having an optical signal bus is disclosed in, e.g., reference [3]. Said optical signal bus consists of a number of parallel fibres in a backplane, on which there are coupled board-shaped circuit modules for mutual interconnection by way of specific connection blocks. An interconnect apparatus having such a signal bus, however, does not permit the desired segmentation in a simple manner.